The tantalum pentahalides are known to be useful as catalysts in various organic reactions. See for example, Friedel-Crafts and Related Reactions, Volume 1, G. A. Olah, Ed., Interscience, 1963, New York. A means of providing tantalum pentahalide distributed over a "support" would be very useful, both from an economic point of view and from a handling point of view. The main problem to date in supporting tantalum (V) halides on a support is that tantalum pentahalides are basically only soluble in solvents in which they react and thus the usual techniques of impregnation to obtain a metal loading of tantalum (V) halide can not be utilized. The instant invention provides a solution to this problem. The process of the instant invention provides for the formation of tantalum (V) chloride/fluoride/oxide bound to the surface of a metal oxide substrate.
The formation of tantalum (V) halide/oxide compositions is the subject matter of a patent filed as application Ser. No. 527,535, on Aug. 29, 1983, and which is now U.S. Pat. No. 4,489,171, issued on Dec. 18, 1984. In U.S. Pat. No. 4,489,171, the tantalum (V) halide/oxide compositions having mixtures of chloride and fluoride were prepared by subliming tantalum pentachloride, reacting the sublimed tantalum pentachloride with a metal oxide substrate, contacting the product therefrom with an oxygen-containing atmosphere and subsequently reacting the product with a fluorinated hydrocarbon. When preparing these mixed chloride and fluoride metal oxide compositions, it was thought necessary, due to thermodynamic considerations, to contact the tantalum (V) chloride/oxide-metal oxide with an oxygen-containing gas or a chemical compound containing oxygen prior to contact with a liquid or gaseous fluorinated hydrocarbon. It has now been found that tantalum (V) chloride/oxide-metal oxide compositions can be converted directly to mixed chloride and fluoride metal oxide compositions without the presence of oxygen, thereby eliminating the problems caused by the presence of oxygen, ie. reaction with oxygen is an exothermic reaction which may damage the catalyst.